How Do Sailboats Work?

From schooners to catamarans to trimarans, these amazing vessels of past and present come in all shapes and sizes. But whether they’re large enough to cross an ocean or small enough for a family outing, each one uses the same fundamental elements that allow it to float and move. In this article, we’ll explore how sailboats work, and how physics principles allow them to harness wind power to move forward.

The sails, of course, are the main source of power for a sailboat. As the boat moves angled to the wind, it generates a force that pushes it sideways. The keel, a long plank submerged underneath the boat’s hull, provides an underwater balancing force against this force. In larger sailboats, the keel also holds ballast to keep it upright in rough water or heavy weather. In smaller boats, the centerboard or daggerboard serves a similar function, and can also be raised or lowered as conditions change.

As the wind hits the sails, a force known as lift creates high air pressure on the outer, convex side of the sails and low pressure on the inner, concave side. Newton’s Third Law, which states that every action has an equal and opposite reaction, describes this force as a backward push that counteracts the original wind force. Another important resistance force comes from turbulence created by the flow of wind and water over the sails and keel. Because turbulence dissipates energy, it increases the resistance of motion by four or five times that of laminar flow.